Aircraft with rotative sustaining blades



I.'\l.8 15l, 1939. H. F. PITCAIRN I h l2,169,849

AIRCRFT 'WITH ROTATIVE SUSTAIHIYHG BDAES Filed. Jan. 8', 19:58

' ATTORNEYS.

Patented VAug'. 15, 1939 UNITED sTATEs PATENT orsi-'CE Harold F. Pitcairn, Bryn Athyn, Pa., assignor, by

mesne assignments,

to Autogiro' Company oi y America, a corporation of Delaware .-Application January 8, 1938, SerlalvNo. 183,925

6 Claims. (Cl. 244-48) This invention relates to lsustaining rotors for aircraft and especially to sustaining rotors capable of autorotation and having some degree of freedom for individual blade movement with re- 5 spect to the hub, (examples of the autorotatable type of rotor being disclosed in Patent No. 1,985,- 819 issued December 25, 1934, to Juan de la Cierva).

In' prior practice, rotorsof this general type l have frequently incorporated several hinges or mounting pivotsA for each blade, including a "drag pivot by means of which the blade is given freedom for at least some degree of lag and lead movement generally within the rotative l path of travel thereof.

'Ihe invention is particularly concerned with a novel type of joint or connection especially adapted to be used in place of the drag hinge of prior practice, although it may be used in place of one or more hinges generally, orl else in conjunction therewith.

One of the important objects of they invention x is the provision of a yieldable or cushioning connection at the'blade root whereby to give the blade the small degree of freedom fory lag and lead movements required in flight (about 1 to 2 each side of center) vand at the same time afford a means for absorbing vibrations and the like.

Although the arrangement of the invention may be applied to existing rotors incorporating a drag hinge or pivot, in accordance with the iii--l vention it is possible even to eliminate the usual drag hinge, as will appear more fully hereinafter.

A further advantage of the invention ilows from the fact that only very small lag and lead move- 1 ments of the bladea're permitted by my improved.

arrangement, in view of-which, the application of `a driving torque to the rotor, as when speeding up the rotor prior to take-off, does not cause substantial angular displacement of the blade.

I The nature, objects and advantages of the invention will be still more apparent from a consideration of the following description referringto the accompanying drawing, in which- 46 Figure 1 is a top plan view of a rotor hub and the root end of an associated blade, with certain l parts shownin horizontal section;

Figure 2 is a transverse sectional view taken as lindicated by the section line 2-2 on Figure` l; 50 Figure 3 is a view similar to Figure 1 but illustrating a modified construction;

Figure i` is also a view similar to Figure 1 ybut showing a further modied arrangement in which the inventionis applied to 'arotor blade mounting befall exstingjifp incorporating a drag pivot; and

` 5-5 of Figure 4.

- at the root end of the blade spar itself.

a pivot Ii.

Figure 5 is a cross sectional view on the line In Figure 1`, the hub is shown at 6, this hub having three apertured lugs 1 for the attachment of three blades, .although it will be understood that any desired number of blades may be employed. In accordance with the invention the blade isprovided with a root end tting 8 having at its inner end anenlargement or bearings with a bearing surface generally of semi-cylin- 10 drlcal shape, the axis of which is generally upright. Alternatively, the bearing 9 may be formed This enlargement is housed between the two halves iiii0 'forming an extension link which is con- 15 nected with one of the hub lugs 1 .by means of The two parts of the extension linkV housing are provided with opposed flanges i2 which may be secured together by bolts I3.

At the cuter side of the bearing 9. the housing 20 is provided with a reduced portion it at each side ofthe tting 8 presenting a rounded vertical ridge to the semi-cylindrical surface of the bearing S. By this means the root end fitting 8 for the blade is permitted freedom -for s'ome rocking 25 movement about the generally upright axis vof the bearing. This arrangement, therefore, provides for lag and lead movements of the blade.

The housing IO-i further includes a sleeve portion l5 extended outboard of the bearing 9 30 in spaced relation to the blade root tting 8 and a ring or sleeve of yieldable material i6 is interposed between these telescopically associated parts. Rubber or some rubber compound may be employed as the yieldablematerial or, if desired, 35 Neoprene may be employed, this material being Y of advantage in this situation because of its high.

hysteresis. A

In connection with the arrangement of Figures 1 and 2, it may be noted that the semi-cylindrical 40 shape of the bearing 9 prevents rotation of the blade about its own longitudinal axis. Maintenance of the desired pitch position of the blade is therefore assured in flight.

In the modified form-shown in Figure 3, the blade root fitting or spar i1 is provided at its inner end with a semi-spherical enlargement or bearing I8`.which cooperates with the inner annular surface i9 of the sleeve 20 in a manner to Relative angular movement of sleeve 2l and blade root' n 1s resisted by the interposioon of fthe invention may be applied to existing blade mountings incorporating a. drag hinge or pivot 25. As here shown, this pivot cooperates with apertured ears 26 and 21 formed respectively on the root end fitting 28 and extension link 29. At its inner end, as before, the extension link is ooupled .to the hub by means of a apping pivot In Figures 4 and 5 it will be seen that a pair of bracket plates "-20 embraces the root end of the blade and extends both inboard and outboard of the axis of drag hinge 25. The cross sectional .shape of these brackets may be clearly seen in .Figure 5, the pair .being bolted together as at 3|. Each bracket is equipped with flanges 32--32 providing a socket for the reception of la resilient or yieldable block of material 23.

When assembled with the bolts 3i drawn up to place the yieidable material under compression, movement of the blade about the drag hinge 25 is very materially restricted.

In all forms illustrated it will be seen that a Pair of' telescopically arranged members is dispod at the blade root and provided with interposed resilient or yielding material for the purpose of cushioning blade movements. In the forms of Figures 1 to \3,vthe two sleeves at the blade root are complete, whereas in the arrangement of Figures 4 and 5, the-brackets 20 in e'ect constitute a split sleeve.

In all forms, in addition to ,providing cushioning action as above notedfthere are provided interengaging metallic bearing surfaces through which the thrust of centrifugal force is trans-V I mitted from the blade to the hub. Thus the cushioning action is obtained without the necessity for carrying the thrust of centrifugal force Vthrough the yieldable material. y

'Ihearrangementsofltigureslto Sareespecisliy'advantageous also because of the material simplincation of structure, as compared with prior arrangements incorporating a drag pivot.

Bull further, it may -benoted that in accordance -1 withl prior practice; it has been common to ern-- ploy a blade' movement controlling device in association with the drag pivot. The yieldable material asaociatedwith the blade root in all forms of this invention -islakmuchfsimpler expedient 'than the damper or control devices heretofore In `with the showing 4ot 1', the

liberatingribs4 ilpcdvidesameansforrestraining the biadeias all-movement except in the lead sensewithrespect to the housing spect tc the .sleeve 2| and mounting memberl Il and, co-incidentally, vaffords absorption of vibra-4 tions substantially in any direction. In this case rotation of the blade about its own longitudinal axis is prevented by employing a reiativelylong resilient sleeve 2|, the interengagement of the resilient material with the root end tting i'l and the sleeve 2li being sufficient to maintain the 5 desired pitch setting` of thc blade under all normal night conditions. Y

As to Figure 4, it may be pointed out'that the arrangement therein shown makes possible application of the invention. to the type of blade mounting incorporating a drag pivot. This adaptation may even be applied to existing equipment of this type.

Iclaim:

1. In an aircraft sustaining rotor having a 15 hub and a blade, mechanism for mounting the blade Aon the hub including a housing havingan enlarged inboard portion and an outboard extension of smaller diameter. a blade root itting having an enlarged thrust carrying inboard por- 20 tion, said iitting being in spaced telescopic relation with the narrower part of said housing and having .its enlargedv portion in bearing contact with an internal surface .of said housing, and yieldable material interposed between said fitting 25 and housing outboard oftheir enlarged portions and throughout a substantial length of their narrower cooperating portions.

2. In an aircraft sustaining rotor having a hub and a blade, mechanism for mounting the blade on the hub including a pair of inter-spaced telescopically associated members one of which is connected with the hub and the other of which is connected with the blade, the outer member being formed of separable parts the meeting lines of which extend generally axially of the blade, resilient material between said members for restricting their relative angular deflection, and

'cooperating interengaging centrifugal load transmitting bearing surfaces on said members. 40

3. In an aircraft sustaining rotor having a hub and a blade, mechanism for mounting the blade on the hub including a pair of inter-spaced telescopically associated members one of which is connected with the hub and the other of which is connected with the blade. resilient material between said members for restricting their relative angular deflection, and cooperating linterensing centrifugal load transmitting bearing surfaces on said members configured to provide line contact therebetween and thereby facilitate seating of said surfaces during relative angular deflection of said members.

4. In an aircraft sustaining rotor having a hub and a blade, mechanism for mounting the blade on the hub including a housing having an enlarged inboard portion and an outboard extension of smaller diameter, a blade root fitting having an enlarged thrust carrying inboard portion with a semi-cylindrical surface the axis of which is at an angle to thelongitudinal blade axis. said tting being in spaced telescopic relation with the narrower portion of said housing and having its semi-cylindrical surface in bearing contact with an .internal surface of said housing, and

on thehubincludingahousing having an. en'

largedinboardilortionwithanannularinternal bearing seatV and an outboard extension' of smaller diameter,- a blade root fitting having an enlarged carrying enlargment of 1I .on the hub including a housing having an ensemi-'spherical shape cooperating with said seat to carry the centrifugal load of the blade in iiig'ht, said tting being in spaced telescopic relation with the narrower part of said' housing,V

and 'yieldable material interposed between said iitting and housing outboard o theirbearing portions and throughout a. substantial length of 4their narrower cooperating portions;

6. Inan 'aircraft sustaining rotor having a hub 10 and. a blade, mechanism'for mounting the blade larged inboardvportion and an outboard extension of smaller diameter removably fastened to said enlarged portion and having an annular bearing seat, a fitting in spaced telescopic relation with the narrower portion of said housing and having a bearing surface cooperating with said bearing seat, and yieldable material interposed between said tting and housing.

' HAROLD F. PITCAIRN. 

